Increased CO2 modifies the carbon balance and the photosynthetic yield of two common Arctic brown seaweeds: Desmarestia aculeata and Alaria esculenta

Ocean acidification affects with special intensity Arctic ecosystems, being marine photosynthetic organisms a primary target, although the consequences of this process in the carbon fluxes of Arctic algae are still unknown. The alteration of the cellular carbon balance due to physiological acclimation to an increased CO2 concentration (1300 ppm) in the common Arctic brown seaweeds Desmarestia aculeata and Alaria esculenta from Kongsfjorden (Svalbard) was analysed. Growth rate of D. aculeata was negatively affected by CO2 enrichment, while A. esculenta was positively affected, as a result of a different reorganization of the cellular carbon budget in both species. Desmarestia aculeata showed increased respiration, enhanced accumulation of storage biomolecules and elevated release of dissolved organic carbon, whereas A. esculenta showed decreased respiration and lower accumulation of storage biomolecules. Gross photosynthesis (measured both as O2 evolution and 14C fixation) was not affected in any of them, suggesting that photosynthesis was already saturated at normal CO2 conditions and did not participate in the acclimation response. However, electron transport rate changed in both species in opposite directions, indicating different energy requirements between treatments and species specificity. High CO2 levels also affected the N-metabolism, and 13C isotopic discrimination values from algal tissue pointed to a deactivation of carbon concentrating mechanisms. Since increased CO2 has the potential to modify physiological mechanisms in different ways in the species studied, it is expected that this may lead to changes in the Arctic seaweed community, which may propagate to the rest of the food web.

Table 2: Areal distribution and specfic mass budget of Hintereisferner

Results of the direct, glaciological determination of the mass budget of Hintereisferner and Kesselwandferner in the Ötztal Alps are summarized for the years 1977/78-1980/81. Tabulations of budget quantities, accumulation and ablation areas are supplemented by graphs of altitudinal and areal distribution of mass balance and by examples of the seasonal course of ablation.

Table 1: Mass budget of Hintereisferner and Kesselwandferner

Results of the direct, glaciological determination of the mass budget of Hintereisferner and Kesselwandferner in the Ötztal Alps are summarized for the years 1075/76-1977/78. Tabulations of budget quantities, accumulation and ablation areas are supplemented by graphs of altitudinal, and areal distribution of mass balance and by examples of the seasonal course of ablation.

Mass balance of Stubacher Sonnblickkees, Hohe Tauern Range, Eastern Alps, Austria

Results of the direct, glaciological determination of the mass budget of Stubacher Sonnblick kees in the Hohe Tauern group are summarized for the years 1971/72 through 1977/78. Tabulation of budget quantities, accumulation and ablation areas and distribution of budget terms for 50 m altitude intervals is supplemented by comments on observations and field work.

Sediment budget of the Laptev Sea, sediment core PS51/092-12, PM9499, PM9462 (Table 2)

This article presents a mass balance calculation of the sediment sources and sinks of the Laptev Sea. Sediment input into three regional sectors calculated on the basis of fluvial sediment discharge and coastal erosion sediment supply is compared with sediment output as estimated from sedimentation rates of well-dated marine sediment cores and data on sediment export to the central Arctic Ocean by sea ice and through bottom currents. Within the uncertainties of the calculations, input and output are very well balanced. The calculation reveals that the sediment budget of the Laptev Sea is mainly controlled by fluvial and coastal sediment input. The major fraction of the material is simply deposited on the Laptev Sea shelf. However, for the western Laptev Sea, where sedimentation rates are low due to the absence of large rivers, export by sea ice is the main output factor.